Means for reducing static electricity charges in nonelectroconductive styli



I Y umw WW 7 H Oct. 23, 1951 D. R. ANDREWS MEANS FOR REDUCING STATIC ELECTRICITY CHARGES IN NONELECTROCONDUCTIVE STYLI Filed June 28, 1947 6 ulh Wm IN V EN TOR. .2241 Alva: .s

,irroe/vi/ Patented Oct. 23, 1951 MEANS FOR REDUCING STATIC ELEC- TRICITY CHARGES IN NONELECTRO- CONDUCTIVE STYLI Dallas R. Andrews, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application June 28, 1947, Serial No. 757,727

'1 Claims. 1

This invention relates to recording devices, and more particularly to a cutting stylus for recording a sound track in a phonograph record.

Phonograph record blanks having lacquer surfaces in which sound grooves may be cut or engraved have been in use for many years. For this purpose, a suitable engraving tool is employed which cuts out of the lacquer surface a thread-like shaving as it forms the sound groove. This shaving has a tendency to curl and frequently winds itself around the cutting tool or stylus, and unless it is removed, it is quite apt to interfere with the recording operation. To accomplish this, there is usually provided a suction line which terminates in proximity to the cutting stylus and draws off the thread as it is formed.

One of the most common materials of which cutter type recording styli are made is sapphire. Since both sapphire and lacquer are non-conductors of electricity, the friction between the front side or cutting face of the sapphire stylus and the lacquer thread as the latter moves upwardly from the disc along the cutting face in the course of the recording operation generates a charge of static electricity on the thread. The charged thread is then so strongly attracted to the neutral disc that the vacuum system frequently is unable to remove the thread satisfactorily,

The primary object of my present invention is to provide an improved recording system in which this difiiculty is obviated.

More particularly, it is an object of my present invention to provide an improved recording stylus of sapphire or other suitable, non-conducting material which will reduce or eliminate the accumulation of a charge of static electricity in the thread and/or disc of lacquer or the like during the recording operation.

Another object of my present invention is to provide an improved recording stylus as aforesaid which will help reduce the load on the thread removing suction system of the recording apparatus so as to enable the suction system to remove waste thread without difficulty.

Still another object of my present invention is to provide a method of converting present day, non-electroconductive styli to accomplish the improved results set forth above.

It is also an object of my present invention to provide an improved recording stylus as aforesaid which is simple in construction, hardly more expensive than conventional recording styli known heretofore, and which is highly efficient in use for the intended purpose. 7

In accordance with my present invention, I

provide on the front or cutting face of a sapphire or other similar non-conducting stylus an electroconductive layer which is connected to a suitable ground point, as through the metallic socket and supporting arm in which the stylus is mounted. As the thread is cut in the blank lacquer disc, it rides up somewhat along the front cutting face of the stylus and therefore is in contact with the aforesaid electroconductive layer. Any static electric charge which is created as a result of the friction between the stylus and the lacquer or other similar, non-conductive record blank will leak off along the above-mentioned electroconductive layer. Thus the thread will not acquire a charge which will cause it to be attracted to the disc, and the suction system will be adequately effective to draw it off.

The novel features characteristic of my invention, as well as additional objects and advantages thereof, will be better understood from the following description, when read in connection with the accompanying drawing in which Figure 1 is a fragmentary, perspective view of a record blank and cutting stylus according to one form of my invention,

Figure 2 is a side elevation of a slightly different form of cutting stylus in accordance with my present invention,

Figure 3 is a front elevation of the stylus shown in Figure 2, and

Figure 4 is a sectional view taken on the line IV-IV of Figure 3.

Referring more particularly to the drawing, there is shown, in Figure 1, a record blank I with which a cutting stylus 3 cooperates to form a sound groove 5 as the blank I rotates in the direction of the arrow A and the stylus 3 is caused to vibrate in well known manner. The blank I may be made of lacquer, Celluloid, Vinylite, wax or any other of the many well known, non-electroconductive materials used heretofore. The stylus 3, which is preferably of sapphire, but may be made of diamond, agate, emerald, hard synthetic resinous material, or any other suitable non-electroconductive material, is formed with a suitably tapered cutting end or point "I of grooveforming configuration, rearwardly extending clearance surfaces 8, and a front cutting face 9 terminating in a sharp cutting edge for cutting out of the blank I a thread I I as the recording operation proceeds. The groove 5 results from the removal of the record blank material represented by the thread I I.

The characteristics of most suitable record materials, and particularly the lacquers used for record blanks, are such that the thread I I thereof tends to curl up after first riding up'along the gaged by said thread.

2. A phonograph recording stylus of the type adapted to remove a thread from a record blank inthecourse of forming a groove therein, said stylus "comprising an elongated body of nonstylus 3 is provided on its front cutting surface 1 9, along the length thereof, with a layer of electroconductive material 13. The layer I3 may be formed by sputtering onto the surface 9 a coating of gold, silver or other, suitable metal, or it may be formed by evaporating chromium' or some other, suitable, hard metal onto the surface 9. Where gold is sputtered onto the surface 9, the gold layer l3 may then be plated with some other, hard metal, since gold is rather soft. Instead of sputtering or plating the layer l3 onto the surface 9, a thin strip of suitable metal may be cemented or other wisesuitably secured thereto. In any case, the layer It will extend up along the front surface 9 of the stylus into engagement with a metallic or other electroconductive socket [5 in which the stylus is securely mounted and which is suitably connected to ground, as through its supporting arm (not 1 shown). Thus, as the thread rides up along the electroconductive surface layer it, any charge of static electricity which may be generated will leak 01]: and-the suction apparatus will have no difficulty in removing the thread II.

In the stylus of Figures 2-4, which is also of non-conductive material, there is provided a longitudinally extending groove ll along the front surface 9, an electroconductive filler l9 being seated in the groove IT. The filler l9 may be constituted by a metallic strip or rod which is cemented in place in the groove H and is preferably finished oif flush with the front surface 9 of the stylus. As in the stylus of Figure 1, the conductive filler [9 has contact with the grounded, conductive socket l5 and it will,-therefore, effectivelycarry off any static charges of electricity generated during the recording operation as the thread H rides up therealong.

From the foregoing description, it will be apparent that I have provided an improved recording stylus which has a distinct advantage over similar styli previously known. Moreover,

it will be apparent that prior art sapphire and similar styli (which are preferred over metallic styli because they retain their sharp cutting edges much longer) can be converted readily into styli according to my present invention by merely applying to the front cuttin surfaces thereof anelectroconductive layer as above described. Although I have shown and described but two forms of styli according to myinvention, it will, no doubt, be apparent to those skilled in the art'that many other forms thereof, as well as changes in those described above, are possible within the spirit of my invention. I therefore desire that the foregoing sh'allbe taken merely as illustrative and not as limiting.

I claim as my invention:

1. A phonograph recording stylus of the type adapted to remove a thread from a record blank in the course of forming a groove therein, said stylus comprising an elongated body 'of 'nonelectroconductive material having a cutting face and rearwardly extending clearance'surelectroconductive material having a cutting face and rearwardly extending clearance surfaces, said cuttingface terminating in a sharp cutting edge having a groove-forming configuration and being engag'eable by said thread during its formation, anda layer of electroconductive material on said cutting face disposed to be engaged by said thread. 7

3. A phonograph recording stylus according to claim 2 wherein said layer of electroconductive material comprises a strip of metal adhered to said cutting face along the length thereof.

4. A phonograph recording stylus of the type adapted to remove a thread from a record blank in the course of forming a groove therein, said stylus comprising a cutter of non-electroconductive material having a cutting face engageable by said thread during its formation, said cutter having a longitudinally extending groove therein at said cutting face, and a filler of electroconductive material in said groove.

5. A phonograph recording stylus according to claim 4 wherein said filler is flush with said cutting face.

6. A phonograph recording stylus according to claim 4 wherein said filler is constituted by a metallic strip seated in said groove.

7. In a phonographic recording device, the combination of an electrically grounded stylus holder, and a cutting stylus carried by said holder for cooperation with a record blank to cut a thread therefrom while forming a groove in said blank, said stylus being of non-electroconductive material and having a cutting face engageable by said thread duringits formation, and an electroconductive member associated with said cutting face and disposed on said stylus in a position to be engaged by said thread, said member having electrical contact with said holder.

DALLAS R. ANDREWS.

REFERENCES CITED The following references are of record in-the file of this patent:

UNITED STATES PATENTS Number Name Date 1,728,167 Olmstead Sept. 10, 1929 1,755,793 Peters Apr. v22, 1930 1,914,659 Olsen i June-20, 1933 2,047,838 Smith et a1. July 14, 1936 2,059,473 Metcalfe Nov. 3, 1936 2,216,970 'Walker 'Oct. 8,1940 2,263,221 Merrill 'Nov. 18, 1941 2,300,923 Hornor 'Nov. 3,1942 2,380,514 Germeshausen July 31, 1945 2,416,202 Naumann Feb. 18, 1947 2,471,601 Albright May 31,1949 2,476,848 Eckhardt et'al. July'19,"194 9 2,493,466 Smith Jan. 3,1950

FOREIGN PATENTS Number Country Date 12,549 Great Britain June-11,1908 

